Automatic population of a join table
I have a join table, called attendance, that combines contacts and events (because one event can have many contacts, and vice versa). I can manually type in the contact and event primary keys into the attendance table (i.e., the customer primary key from the customer table goes to the customer foreign key in the attendance table). This works fine and, based on this, I can then create a portal in a given contact's record, showing what events they have attended.
But this is prohibitively slow, and I need to populate many attendance records at once by brining in a large group of records from the contacts table, combined with an event from the event tables.
Any clues on how to do this would be much appreciated (it seems the process may require the use of a scrip, an area I'm only now learning about).